The 2-1 decision by a Patent Office administrative tribunal followed decades of criticism of the Washington club by Native Americans and others who say the name is a slur. The club said it would appeal the ruling.

Five Native Americans had petitioned to overturn six Redskins trademarks, and evidence presented to the tribunal showed that "Redskins" was disparaging, the Patent Office said in a statement.

"Thus, the federal registrations for the 'Redskins' trademarks involved in this proceeding must be canceled," the agency said.

The ruling does not mean that the trademarks can no longer be used by the NFL club, only that they are no longer registered. The trademark protection remains until appeals are completed.

The decision strips the franchise of legal presumption of ownership and the ability to use the federal trademark symbol, and block importation of counterfeit Redskins goods.

Bob Raskopf, a trademark attorney for the Redskins, said the club would appeal the ruling to federal court. He said the case was the same as one in which the tribunal canceled the Redskins' trademarks in 1999.

A court overturned that decision on appeal, saying the petitioners had waited too long to assert their rights after the first Redskins' trademark was issued in 1967.

"We are confident we will prevail once again," Raskopf said in a statement.

The NFL, the most popular sports league in the United States, declined to comment and referred reporters to Raskopf's statement.

Citing tradition, team owner Daniel Snyder for 14 years has defied calls to change the club's name and Indian head logo, which date from the 1930s.

The decision drew praise from the Oneida Indian Nation and the National Congress of American Indians (NCAI), which have campaigned against the Redskins' name.

The ruling will prompt a name change "if only because it imperils the ability of the team's billionaire owner to keep profiting off the denigration and dehumanization of Native Americans," Oneida Indian Nation Representative Ray Halbritter and NCAI Executive Director Jackie Pata said in a statement.

Half the U.S. Senate, all of them Democrats, last month urged the NFL to endorse a name change for the franchise. Senate Majority Leader Harry Reid of Nevada and Senator Maria Cantwell of Washington state, both signers of the letter, applauded the tribunal's decision on the Senate floor.

"Daniel Snyder may be the last person in the world to realize this, but it's just a matter of time until he is forced to do the right thing and change the name," Reid said.

President Barack Obama also has weighed in, saying before the ruling that if he owned the team he would consider changing the name.

NFL Commissioner Roger Goodell said in January that most football fans and Americans supported the Redskins keeping their name.

The named petitioner in the case, Blackhorse v. Pro Football Inc, is Amanda Blackhorse, a Navajo psychiatric social worker.

In a USA Today profile this year, Blackhorse said she had considered what she might say to Snyder if she ever met him.

"I'd ask him, 'Would you dare call me a redskin, right here, to my face?'" she said. "And I suspect that, no, he would not do that." (Reporting by Ian Simpson and Steve Ginsburg; Editing by Jim Loney)